By Lee Chi-dong SEOUL, June 1 (Yonhap) -- President Lee Myung-bak instructed his Cabinet Tuesday to come up with a long-term strategy for the reunification of the Korean Peninsula, despite heightened military tensions following the sinking of a South Korean warship in March.

"National security has emerged as an important task since the Cheonan incident," Lee said at a weekly Cabinet meeting. "With regard to security, people usually think of confrontation. Fundamentally, however, we should draw up a strategy on security bearing reunification in mind."

Lee's comments came as the South pushes for non-military reprisals against the North over the naval tragedy. An international team of investigators concluded that a stealthy North Korean submarine had mounted a torpedo attack on the Cheonan, a 1,200-ton patrol ship, on March 26, bringing it down and killing 46 sailors onboard.

Pyongyang has threatened military retaliation against any punishment, denying its involvement in the incident.

The 1950-1953 Korean War technically has not ended for the divided sides who signed an armistice at the end of the conflict, not a peace treaty.

Lee also said he remains determined to carry on domestic reform measures after Wednesday's local elections.

"Once the elections end tomorrow, I will advance the overall system of our society to make South Korea a top-level country," the president said according to his spokeswoman Kim Eun-hye. "Regardless of the results of the elections, we will have to concentrate on our tasks."